Document Detail


Luminescence and stability of aqueous thioalkyl acid capped CdSe/ZnS quantum dots correlated to ligand ionization.
MedLine Citation:
PMID:  17274093     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
The spectroscopic properties of CdSe/ZnS quantum dots (QDs) were observed to change as a function of thioalkyl acid ligand. Experiments were performed using 2, 3, 6, and 11-carbon linear thioalkyl acids, as well as mercaptosuccinic acid (MSA) and dihydrolipoic acid (DHLA). Bathochromic shifts of up to 14 nm in the emission spectra of QDs capped with these ligands were observed. Similarly, hypsochromic or bathochromic shifts up to 7 nm were observed for a specific ligand in acidic or basic solution, respectively. These shifts could be correlated to the number of ionized ligands and the ability of the ligands to act as hole acceptors. It was also found that differences in quantum yield between the ligands were primarily due to variations in radiative decay rate and not nonradiative decay rate. This indicated that different degrees of QD surface passivation were not responsible for the differences, and that the radiative system must be considered as the sum of the ligands and the QD nanocrystal. The stability of QDs capped with mercaptoacetic acid, MSA, and DHLA towards aggregation at low pH was found to correlate with the pK(a) of the ligands. Spectral shifts were also observed during aggregation. Overall, the luminescence of thioalkyl acid capped QDs appears to be a complex function of dielectric constant, electrostatic or hole-acceptor interactions with ionized ligands, and, to a lesser extent, passivation.
Authors:
W Russ Algar; Ulrich J Krull
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Chemphyschem : a European journal of chemical physics and physical chemistry     Volume:  8     ISSN:  1439-4235     ISO Abbreviation:  Chemphyschem     Publication Date:  2007 Mar 
Date Detail:
Created Date:  2007-03-19     Completed Date:  2007-04-27     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100954211     Medline TA:  Chemphyschem     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  561-8     Citation Subset:  -    
Affiliation:
Chemical Sensors Group, Department of Chemical and Physical Sciences, University of Toronto at Mississauga, 3359 Mississauga Rd. North, Mississauga, ON L5 L 1C6, Canada.
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